1. Field
One or more exemplary embodiments relate to a pressure sensor or a contact force sensor that uses a Wheatstone bridge, and more particularly, to a technology for increasing performance of a sensor including a Wheatstone bridge that is insensitive to a temperature change.
2. Description of the Related Art
Pressure sensors or contact force sensors generally include a Wheatstone bridge, which is a particular type of electrical circuit. FIG. 1 is an equivalent circuit diagram of a conventional Wheatstone bridge. The conventional Wheatstone bridge basically comprises four resistors R1 through R4. Although the four resistors R1 through R4 are generally designed to have the same value, in actuality they have different values due to inconsistencies occurring in the actual manufacturing processes thereof. Also, the values of the four resistors R1 through R4 vary according to a temperature change thereof, e.g., due to variations in the ambient temperature of the environment in which the conventional Wheatstone bridge is disposed. Therefore, when a pressure or load is not externally applied to a piston bridge during an initial stage, an offset occurs between Vop and Von. A sensor that uses the Wheatstone bridge differentially amplifies voltages of Vop and Von using a high amplification end in order to obtain good output sensitivity. Thus, an initial offset between Vop and Von is further amplified at a final output end due to a high amplification rate, which unwontedly reduces an output span of the sensor or undesirably causes saturation.